Lecture 5. Interstellar Dust: Optical Properties
|
|
- Emmeline French
- 6 years ago
- Views:
Transcription
1 Lecture 5. Interstellar Dust: Optical Properties 1. Introduction 2. Extinction 3. Mie Scattering 4. Dust to Gas Ratio 5. Appendices References Spitzer Ch. 7, Osterbrock Ch. 7 DC Whittet, Dust in the Galactic Environment (IoP, 2002) E Krugel, Physics of Interstellar Dust (IoP, 2003) B Draine, ARAA, 41, 241, 2003
2 1. Introduction: Brief History of Dust Nebular gas long accepted but existence of absorbing interstellar dust controversial. Herschel ( ) found few stars in some directions, later extensively demonstrated by Barnard s photos of dark clouds. Trumpler (PASP ) conclusively demonstrated interstellar absorption by comparing luminosity distances & angular diameter distances for open clusters: Angular diameter distances are systematically smaller Discrepancy grows with distance Distant clusters are redder Estimated ~ 2 mag/kpc absorption Attributed it to Rayleigh scattering by gas
3 Some of the Evidence for Interstellar Dust Extinction (reddening of bright stars, dark clouds) Polarization of starlight Scattering (reflection nebulae) Continuum IR emission Depletion of refractory elements from the gas Dust is also observed in the winds of AGB stars, SNRs, young stellar objects (YSOs), comets, interplanetary Dust particles (IDPs), and in external galaxies. The extinction varies continuously with wavelength and requires macroscopic absorbers (or dust particles).
4 Examples of the Effects of Dust Extinction B68 Scattering - Pleiades
5 Extinction: Some Definitions Optical depth, cross section, & efficiency: τ λ ext = n dust σ ext λ ds = σ λ ext n dust = πa 2 Q ext (λ) N dust n d is the volumetric dust density The magnitude of the extinction A λ : [ ] I(λ) = I 0 (λ) exp τ λ ext A λ = 2.5log 10 [ I(λ)/I 0 (λ)] ext ext = 2.5log 10 (e)τ λ =1.086τ λ
6 2. Extinction (Continuum Opacity) General Properties 1. uniform shape 2. λ -1 trend in the optical/nir 3. steep UV rise with peak at ~ 800 Å 4. spectral features: λ = 220 nm λ = 47 nm λ = 9.7 µm, λ ~ 2-3 µm 5. polarization with large extinction UV Optical IR 220 nm bump Magnitudes of extinction vs, wavelength (schematic)
7 Extinction = Scattering + Absorption For spherical grains, define efficiencies, Q ext, Q sca,q abs such that Q ext =Q sca +Q abs σ abs = Q abs πa 2 σ sca = Q sca πa 2 σ ext = Q ext πa 2 = (Q abs + Q sca )πa 2 albedo = σ sca σ ext = Q sca Q ext 1
8 Scattering Phase Function The scattered intensity is a function of the angle θ between the incident and scattered wave, and is quantified by the phase function g g = cosθ = π 0 I(θ)cosθdΩ π 0 I(θ)dΩ θ Isotropic scattering cosθ = 0 Forward scattering cosθ = 1 Back scattering cosθ = -1
9 Measuring the Extinction The absolute extinction requires the distance & absolute magnitude, m λ = M λ + 5 log d A λ. ; instead use: The relative extinction or selective extinction is deduced from observations of reddened stars of known spectral type, i.e., starting from the known color excess, (B-V) 0 E(B-V) = A(B)-A(V) = (B-V) - (B-V) 0 The normalized extinction, 1/R V, measures the steepness of the extinction R V = A(V) / [A(B)-A(V)] = A(V) / E(B-V) It is steep in the diffuse ISM: R V = 3.1±0.2, shallower in dark clouds: R V 5
10 Copernicus Observations of Two Similar Stars Raw (uncorrected, unnormalized) count rates from the UV satellite for two O7 stars, S Mon (top, un-reddened ) ξ Per (bottom, reddened ). Upper panel: Å Bottom panel : Å
11 Representative Interstellar Extinction Curves Based on extinction measurements from bands from UV to NIR Reference: Fitzpatrick, PASP 111, 63, 1999 & Draine, ARAA, 41, 241, 2003
12 Empirical Extinction to Gas Ratio The extinction measurements for the diffuse interstellar medium yield a constant extinction to gas ratio for diffuse clouds near the Sun (with R V 3.1): A (V) N H / 2 x mag cm -2 This suggests that the dust-to-gas mass ratio is approximately constant since A(V) is related to the column density of the absorbing dust: A(V) = n d s σ ext = N d σ ext Dividing by the gas column, N H = n H s, yields the mean extinction cross section per H nucleus < n d /n H σ ext > ~ 5 x cm 2 See also Appendix 3.
13 3. Electromagnetic Scattering by Small Particles AN Mie (Ann Phys ), considering uniform spheres of radius a with any index of refraction m = n - i k with m = m (λ), used a multipole expansion of the scattered wave ( vector spherical harmonics times radial Bessel functions) and applied boundary conditions at the surface of the sphere to get E and B for all space. Best reference is: HC van de Hulst, Light Scattering from Small Particles Basic parameter: x = 2πa/λ x << 1: long wavelengths; need only a few terms diffraction limit x >> 1: short wavelengths; need many terms geometrical optics limit
14 Asymptotic Formulae For x << 1 Q abs = 4xIm m2 1 λ 1 m Q sca = 8 3 x 4 m 2 1 Re m λ 4 In this (long wavelength) limit, the absorption cross section depends only on the mass of the grain: σ abs = Q abs πa 2 a 3 m dust (Rayleigh scattering) We need to be able to calculate the optical properties of a wide variety of dust particle models in order to deduce the physical properties of IS dust from the observed extinction.
15 Pure vs. Dirty Dielectrics Q ext =Q sca Q ext Q sca
16 Angular Distributions (m = 1.33) The angular distribution becomes highly peaked in the forward direction for x >> 1. Note the difference between the E field perpendicular and parallel to the scattering plane.
17 4. Dust to Gas Ratio (Purcell 1969) Use the Kramers-Kronig relation (ApJ ) to relate the integrated extinction coefficient for spherical grains with constant index m to the dust column N d Q ext dλ = 4π 2 a m2 1 0 m τ ext = Q ext πa 2 N d, N d = ρ d L /m d m 2 1 τ ext dλ = 4π 3 a 3 N 0 d m (only a lower limit on grain volume for other shapes) Reintroduce the measured A λ A λ =1.086τ λ =1.086Q ext πa 2 N d
18 0 Gas to Dust Ratio (cont d) A λ dλ = 3π m2 1 n L m 2 d V gr + 2 n d V gr = n d m gr m gr /V gr = ρ d ρ gr = where V gr = (4π/3) a 3. average dust density density of solid NB error: π 3 -> π 2 The average extinction A λ (lower limit to integral) gives the mean dust density. Dividing the integral by mn H = mn H /L, gives the mean dust to gas mass ratio (m = gas particle mass) For example, assuming silicate dust with real index = 1.5 & ρ gr = 2.5 g cm -3 yields: ρ d / ρ g =
19 Implications of Interstellar Abundances With ρ d / ρ g = 0.006, a significant fraction of O and the refractories is locked up in interstellar dust, unless the present (compact, spherical) grain model is grossly incorrect. For reference, the mass fraction of heavy elements Z = (solar) and Z = (B stars / ISM). Many attempts have been made to make composition models within the abundance budget, e.g., typically Silicates: Mg, Si, Fe(95%), O (20%) in (Mg,Fe) 2 SiO 4 Carbonaceous material (graphite & organics): C (60%) plus some SiC
20 Exemplary Interstellar Dust Composition Element Abundance A M/M H C 0.6 x Mg Fe Si O Total NB Both the abundances and the fractions of O and C used in this example are probably too high.
21 Another Interstellar Dust Composition Element Abundance A M/M H C 0.25 x Mg Fe Si O Total NB Here we ve used the interstellar abundances from Lecture 01 and also adjusted the fractions of O and C, the latter from Draine s 2003 review article.
22 Appendix 1. Selective Extinction
23 Appendix 2. Combining Average Extinction and Gas Measurements
24 Appendix 3 Poor Man s Estimate of the Dust to Gas Ratio
7. Dust Grains & Interstellar Extinction. James R. Graham University of California, Berkeley
7. Dust Grains & Interstellar Extinction James R. Graham University of California, Berkeley Visual Extinction Presence of interstellar gas or nebulae has a long history Existence of absorbing interstellar
More informationDust in the Diffuse Universe
Dust in the Diffuse Universe Obscuring Effects Chemical Effects Thermal Effects Dynamical Effects Diagnostic Power Evidence for Grains: Chemical Effects Catalyzes molecular hydrogen formation. Depletion
More informationAstrochemistry (2) Interstellar extinction. Measurement of the reddening
Measurement of the reddening The reddening of stellar colours casts light on the properties of interstellar dust Astrochemistry (2) Planets and Astrobiology (2016-2017) G. Vladilo The reddening is measured
More informationInterstellar Dust and Extinction
University of Oxford, Astrophysics November 12, 2007 Outline Extinction Spectral Features Emission Scattering Polarization Grain Models & Evolution Conclusions What and Why? Dust covers a range of compound
More informationDust. The four letter word in astrophysics. Interstellar Emission
Dust The four letter word in astrophysics Interstellar Emission Why Dust Dust attenuates and scatters UV/optical/NIR Amount of attenuation and spectral shape depends on dust properties (grain size/type)
More informationThe Dusty Universe. Joe Weingartner George Mason University Dept of Physics and Astronomy
The Dusty Universe Joe Weingartner George Mason University Dept of Physics and Astronomy To astronomers, dust means: sub micron solid grains (1 micron = 1 m = 10 6 m = one millionth of a meter) Typical
More information8: Composition and Physical state of Interstellar Dust
8: Composition and Physical state of Interstellar Dust James Graham UC, Berkeley 1 Reading Tielens, Interstellar Medium, Ch. 5 Mathis, J. S. 1990, AARA, 28, 37 Draine, B. T., 2003, AARA, 41, 241 2 Nature
More informationLecture 5. Interstellar Dust: Chemical & Thermal Properties
Lecture 5. Interstellar Dust: Chemical & Thermal Properties!. Spectral Features 2. Grain populations and Models 3. Thermal Properties 4. Small Grains and Large Molecules -------------------------------------------------
More informationA Far-ultraviolet Fluorescent Molecular Hydrogen Emission Map of the Milky Way Galaxy
A Far-ultraviolet Fluorescent Molecular Hydrogen Emission Map of the Milky Way Galaxy (The Astrophysical Journal Supplement Series, 231:21 (16pp), 2017 August) November 14, 2017 Young-Soo Jo Young-Soo
More informationLecture 6: Continuum Opacity and Stellar Atmospheres
Lecture 6: Continuum Opacity and Stellar Atmospheres To make progress in modeling and understanding stellar atmospheres beyond the gray atmosphere, it is necessary to consider the real interactions between
More informationStars, Galaxies & the Universe Lecture Outline
Stars, Galaxies & the Universe Lecture Outline A galaxy is a collection of 100 billion stars! Our Milky Way Galaxy (1)Components - HII regions, Dust Nebulae, Atomic Gas (2) Shape & Size (3) Rotation of
More informationASTR2050 Spring Please turn in your homework now! In this class we will discuss the Interstellar Medium:
ASTR2050 Spring 2005 Lecture 10am 29 March 2005 Please turn in your homework now! In this class we will discuss the Interstellar Medium: Introduction: Dust and Gas Extinction and Reddening Physics of Dust
More informationPhysics and chemistry of the interstellar medium. Lecturers: Simon Glover, Rowan Smith Tutor: Raquel Chicharro
Physics and chemistry of the interstellar medium Lecturers: Simon Glover, Rowan Smith Tutor: Raquel Chicharro This course consists of three components: Lectures Exercises Seminar [Wed., 2-4] [Thu., 4-5]
More informationDust. Interstellar Emission. The four letter word in astrophysics Scattered in S&G mostly pgs , MBW
Dust The four letter word in astrophysics Scattered in S&G mostly pgs 100-108, MBW 478-482 recent conference Proceedings of the International Astronomical Porous chondrite interplanetary dust particle.
More informationInterstellar Dust and Gas
Interstellar Dust and Gas In 1783 William Herschel began a survey of the heavens using an 18 ¾ inch reflector of his own construction. His goal was to discover new star clusters, nebulae, and double stars.
More informationSubstellar Atmospheres II. Dust, Clouds, Meteorology. PHY 688, Lecture 19 Mar 11, 2009
Substellar Atmospheres II. Dust, Clouds, Meteorology PHY 688, Lecture 19 Mar 11, 2009 Outline Review of previous lecture substellar atmospheres: opacity, LTE, chemical species, metallicity Dust, Clouds,
More informationTHE GALAXY. Spitzer Space Telescope Images & Spectra: 3µm - 170µm
THE GALAXY Composite infrared colour image of Galactic Centre region taken at 1.25, 2.2 and 3.5 microns with COBE/DIRBE instrument (NASA/GSFC). GALAXY: A conglomeration of stars, gas + dust Topics: Star
More informationThe Interstellar Medium
http://www.strw.leidenuniv.nl/~pvdwerf/teaching/ The Interstellar Medium Lecturer: Dr. Paul van der Werf Fall 2014 Oortgebouw 565, ext 5883 pvdwerf@strw.leidenuniv.nl Assistant: Kirstin Doney Huygenslaboratorium
More informationDust: Optical Theory Wednesday, January 26, 2011
Dust: Optical Theory Wednesday, January 6, 11 CONTENTS: 1. Introduction. Optics of Spherical Grains A. Absorption & Scattering: Long- Wavelength Limit B. Absorption & Scattering: Short- Wavelength Limit
More information3 reasons it was hard to figure out that we are in a Galaxy
Prof. Jeff Kenney Class 10 October 3, 2016 3 reasons it was hard to figure out that we are in a Galaxy 1. it's big -- one needs sensitive telescopes to see (individual stars) across the Galaxy 2. we're
More informationInterstellar Medium and Star Birth
Interstellar Medium and Star Birth Interstellar dust Lagoon nebula: dust + gas Interstellar Dust Extinction and scattering responsible for localized patches of darkness (dark clouds), as well as widespread
More informationThe Physics of the Interstellar Medium
The Physics of the Interstellar Medium Ulrike Heiter Contact: 471 5970 ulrike@astro.uu.se www.astro.uu.se Matter between stars Average distance between stars in solar neighbourhood: 1 pc = 3 x 1013 km,
More informationInterstellar Medium by Eye
Interstellar Medium by Eye Nebula Latin for cloud = cloud of interstellar gas & dust Wide angle: Milky Way Summer Triangle (right) α&β Centauri, Coal Sack Southern Cross (below) Dust-Found in the Plane
More informationMeasurement of the stellar irradiance
Measurement of the stellar irradiance Definitions Specific Intensity : (monochromatic) per unit area normal to the direction of radiation per unit solid angle per unit wavelength unit (or frequency) per
More informationLecture 18 - Photon Dominated Regions
Lecture 18 - Photon Dominated Regions 1. What is a PDR? 2. Physical and Chemical Concepts 3. Molecules in Diffuse Clouds 4. Galactic and Extragalactic PDRs References Tielens, Ch. 9 Hollenbach & Tielens,
More informationDust Formation History with Galaxy Evolution
Dust Formation History with Galaxy Evolution Tsutomu T. TAKEUCHI Division of Particle and Astrophysical Science, Nagoya University, Japan ESTEC, 14 Nov., 2014, the Netherlands 1. Introduction What are
More information6. Interstellar Medium. Emission nebulae are diffuse patches of emission surrounding hot O and
6-1 6. Interstellar Medium 6.1 Nebulae Emission nebulae are diffuse patches of emission surrounding hot O and early B-type stars. Gas is ionized and heated by radiation from the parent stars. In size,
More informationInterstellar Dust and Gas
Interstellar Dust and Gas In 1783 William Herschel began a survey of the heavens using an 18 ¾ inch reflector of his own construction. His goal was to discover new star clusters, nebulae, and double stars.
More informationAstr 2310 Thurs. March 23, 2017 Today s Topics
Astr 2310 Thurs. March 23, 2017 Today s Topics Chapter 16: The Interstellar Medium and Star Formation Interstellar Dust and Dark Nebulae Interstellar Dust Dark Nebulae Interstellar Reddening Interstellar
More informationSIMPLE RADIATIVE TRANSFER
ASTR 511/O Connell Lec 4 1 SIMPLE RADIATIVE TRANSFER The theory of radiative transfer provides the means for determining the emergent EM spectrum of a cosmic source and also for describing the effects
More informationSome HI is in reasonably well defined clouds. Motions inside the cloud, and motion of the cloud will broaden and shift the observed lines!
Some HI is in reasonably well defined clouds. Motions inside the cloud, and motion of the cloud will broaden and shift the observed lines Idealized 21cm spectra Example observed 21cm spectra HI densities
More informationDust: Grain Populations, Extinction Curves, and Emission Spectra Monday, January 31, 2011
Dust: Grain Populations, Extinction Curves, and Emission Spectra Monday, January 31, 2011 CONTENTS: 1. Introduction 2. The Extinction Curve and Abundance Constraints A. Formalities B. Features 3. Infrared
More informationThe Milky Way, Our galaxy
The Milky Way, Our galaxy Diffuse Band of light that crosses the Sky in the North Galileo: it s faint stars Early speculation and fleshing out where we are 1 Milky Way from Zuerich Milky Way from Australia
More informationUniverse Now. 9. Interstellar matter and star clusters
Universe Now 9. Interstellar matter and star clusters About interstellar matter Interstellar space is not completely empty: gas (atoms + molecules) and small dust particles. Over 10% of the mass of the
More informationLecture 2 Line Radiative Transfer for the ISM
Lecture 2 Line Radiative Transfer for the ISM Absorption lines in the optical & UV Equation of transfer Absorption & emission coefficients Line broadening Equivalent width and curve of growth Observations
More informationDiffuse Interstellar Medium
Diffuse Interstellar Medium Basics, velocity widths H I 21-cm radiation (emission) Interstellar absorption lines Radiative transfer Resolved Lines, column densities Unresolved lines, curve of growth Abundances,
More informationReminders! Observing Projects: Both due Monday. They will NOT be accepted late!!!
Reminders! Website: http://starsarestellar.blogspot.com/ Lectures 1-15 are available for download as study aids. Reading: You should have Chapters 1-14 read. Read Chapters 15-17 by the end of the week.
More informationStellar Winds: Mechanisms and Dynamics
Astrofysikalisk dynamik, VT 010 Stellar Winds: Mechanisms and Dynamics Lecture Notes Susanne Höfner Department of Physics and Astronomy Uppsala University 1 Most stars have a stellar wind, i.e. and outflow
More informationThe Milky Way Galaxy and Interstellar Medium
The Milky Way Galaxy and Interstellar Medium Shape of the Milky Way Uniform distribution of stars in a band across the sky lead Thomas Wright, Immanuel Kant, and William Herschel in the 18th century to
More informationFrom theory to observations
Stellar Objects: From theory to observations 1 From theory to observations Given the stellar mass and chemical composition of a ZAMS, the stellar modeling can, in principle, give the prediction of the
More informationThe Interstellar Medium (ch. 18)
The Interstellar Medium (ch. 18) The interstellar medium (ISM) is all the gas (and about 1% dust) that fills our Galaxy and others. It is the raw material from which stars form, and into which stars eject
More informationGalactic dust in the Herschel and Planck era. François Boulanger Institut d Astrophysique Spatiale
Galactic dust in the Herschel and Planck era François Boulanger Institut d Astrophysique Spatiale Motivation Dust emission Dust models Dust life cycle Planck early results Dust polarisation Outline Dust
More informationLecture 26. Regional radiative effects due to anthropogenic aerosols. Part 2. Haze and visibility.
Lecture 26. Regional radiative effects due to anthropogenic aerosols. Part 2. Haze and visibility. Objectives: 1. Attenuation of atmospheric radiation by particulates. 2. Haze and Visibility. Readings:
More informationThe mathematics of scattering and absorption and emission
The mathematics of scattering and absorption and emission The transmittance of an layer depends on its optical depth, which in turn depends on how much of the substance the radiation has to pass through,
More informationInterstellar Dust Clouds UROP Spring 2013 Chris Nolting Faculty Mentor: Professor Terry Jones 5/17/13
Interstellar Dust Clouds UROP Spring 2013 Chris Nolting Faculty Mentor: Professor Terry Jones 5/17/13 Using infrared observations of L1544, a dark cloud in the Taurus Molecular Complex, density maps were
More informationPhysics and Chemistry of the Interstellar Medium
Physics and Chemistry of the Interstellar Medium Sun Kwok The University of Hong Kong UNIVERSITY SCIENCE BOOKS Sausalito, California * Preface xi The Interstellar Medium.1.1 States of Matter in the ISM
More informationPhysics 224 The Interstellar Medium
Physics 224 The Interstellar Medium Lecture #11: Dust Composition, Photoelectric Heating, Neutral Gas Outline Part I: Dust Heating & Cooling continued Part III: Dust Emission & Photoelectric Heating Part
More informationRadiation from planets
Chapter 4 Radiation from planets We consider first basic, mostly photometric radiation parameters for solar system planets which can be easily compared with existing or future observations of extra-solar
More informationDust [12.1] Star clusters. Absorb and scatter light Effect strongest in blue, less in red, zero in radio.
More abs. Dust [1.1] kev V Wavelength Optical Infra-red More abs. Wilms et al. 000, ApJ, 54, 914 No grains Grains from http://www.astro.princeton.edu/~draine/dust/dustmix.html See DraineH 003a, column
More informationExploring ISM dust with IRSIS. Emmanuel DARTOIS IAS-CNRS
Exploring ISM dust with IRSIS Emmanuel DARTOIS IAS-CNRS IRSIS meeting 05-12-2007 Overview Intestellar ice mantles Hydrocarbons in the galaxy and outside Polycyclic Aromatic Hydrocarbons (PAHs) Interstellar
More informationLec 3. Radiative Processes and HII Regions
Lec 3. Radiative Processes and HII Regions 1. Photoionization 2. Recombination 3. Photoionization-Recombination Equilibrium 4. Heating & Cooling of HII Regions 5. Strömgren Theory (for Hydrogen) 6. The
More informationNIR Silicate features and Statistics from IRAS data
NIR Silicate features and Statistics from IRAS data Ranjan Gupta Inter University Center for Astronomy and Astrophysics Pune-411007, India NIR Silicate features and Statistics from IRAS data p.1/46 Abstract
More informationAstronomy 113. Dr. Joseph E. Pesce, Ph.D. Distances & the Milky Way. The Curtis View. Our Galaxy. The Shapley View 3/27/18
Astronomy 113 Dr. Joseph E. Pesce, Ph.D. Distances & the Milky Way 14-2 Historical Overview: the Curtis-Shapley Debate ³What is the size of our galaxy? ³What is the nature of spiral nebula? The Curtis
More informationAstronomy 113. Dr. Joseph E. Pesce, Ph.D. Dr. Joseph E. Pesce, Ph.D.
Astronomy 113 Dr. Joseph E. Pesce, Ph.D. Distances & the Milky Way Historical Overview: the Curtis-Shapley Debate ³What is the size of our galaxy? ³What is the nature of spiral nebula? 14-2 ³Occurred in
More informationScattering of EM waves by spherical particles: Overview of Mie Scattering
ATMO 551a Fall 2010 Scattering of EM waves by spherical particles: Overview of Mie Scattering Mie scattering refers to scattering of electromagnetic radiation by spherical particles. Under these conditions
More informationStars AS4023: Stellar Atmospheres (13) Stellar Structure & Interiors (11)
Stars AS4023: Stellar Atmospheres (13) Stellar Structure & Interiors (11) Kenneth Wood, Room 316 kw25@st-andrews.ac.uk http://www-star.st-and.ac.uk/~kw25 What is a Stellar Atmosphere? Transition from dense
More informationGas 1: Molecular clouds
Gas 1: Molecular clouds > 4000 known with masses ~ 10 3 to 10 5 M T ~ 10 to 25 K (cold!); number density n > 10 9 gas particles m 3 Emission bands in IR, mm, radio regions from molecules comprising H,
More informationThe Origin and Nature of Dust in Core Collapse Supernovae
The Origin and Nature of Dust in Core Collapse Supernovae Eli Dwek Goddard Space Flight Center HST image of the Carina Nebula removal from the ISM by star formation formation in stellar winds and ejecta
More informationStellar evolution Part I of III Star formation
Stellar evolution Part I of III Star formation The interstellar medium (ISM) The space between the stars is not completely empty, but filled with very dilute gas and dust, producing some of the most beautiful
More informationChapter 7: From theory to observations
Chapter 7: From theory to observations Given the stellar mass and chemical composition of a ZAMS, the stellar modeling can, in principle, predict the evolution of the stellar bolometric luminosity, effective
More informationThe physics of stars. A star begins simply as a roughly spherical ball of (mostly) hydrogen gas, responding only to gravity and it s own pressure.
Lecture 4 Stars The physics of stars A star begins simply as a roughly spherical ball of (mostly) hydrogen gas, responding only to gravity and it s own pressure. X-ray ultraviolet infrared radio To understand
More informationClicker Question: Clicker Question: What is the expected lifetime for a G2 star (one just like our Sun)?
How Long do Stars Live (as Main Sequence Stars)? A star on Main Sequence has fusion of H to He in its core. How fast depends on mass of H available and rate of fusion. Mass of H in core depends on mass
More informationPhysics of Interstellar Dust
Physics of Interstellar Dust 1. Optics of Small Particles 2. Inferred Size Distributions for Interstellar Grains 1 B.T. Draine Physics of Interstellar Dust IPMU 2010.04.21 SRK Lecture in class Review:
More informationGuiding Questions. Stellar Evolution. Stars Evolve. Interstellar Medium and Nebulae
Guiding Questions Stellar Evolution 1. Why do astronomers think that stars evolve? 2. What kind of matter exists in the spaces between the stars? 3. What steps are involved in forming a star like the Sun?
More informationAstronomy 1 Fall 2016
Astronomy 1 Fall 2016 Lecture11; November 1, 2016 Previously on Astro-1 Introduction to stars Measuring distances Inverse square law: luminosity vs brightness Colors and spectral types, the H-R diagram
More informationX-ray Studies of Interstellar and Intergalactic Dust
X-ray Studies of Interstellar and Intergalactic Dust Lia Corrales Columbia University NASA Earth and Space Science Fellow Advised by Frits Paerels X-ray scattering tools for studying the ISM Cygnus X-3:
More informationFrom theory to observations
Stellar Objects: From theory to observations 1 From theory to observations Update date: December 13, 2010 Given the stellar mass and chemical composition of a ZAMS, the stellar modeling can, in principle,
More informationAstronomy 114. Lecture 27: The Galaxy. Martin D. Weinberg. UMass/Astronomy Department
Astronomy 114 Lecture 27: The Galaxy Martin D. Weinberg weinberg@astro.umass.edu UMass/Astronomy Department A114: Lecture 27 18 Apr 2007 Read: Ch. 25,26 Astronomy 114 1/23 Announcements Quiz #2: we re
More informationRadiation in the atmosphere
Radiation in the atmosphere Flux and intensity Blackbody radiation in a nutshell Solar constant Interaction of radiation with matter Absorption of solar radiation Scattering Radiative transfer Irradiance
More informationDynamical Atmospheres & Winds of AGB Stars A Theorist's View
Dynamical Atmospheres & Winds of AGB Stars A Theorist's View Susanne Höfner Department of Physics & Astronomy Uppsala University Dynamics of atmosphere & wind stellar pulsation & convection induce strong
More informationPART 3 Galaxies. Gas, Stars and stellar motion in the Milky Way
PART 3 Galaxies Gas, Stars and stellar motion in the Milky Way The Interstellar Medium The Sombrero Galaxy Space is far from empty! Clouds of cold gas Clouds of dust In a galaxy, gravity pulls the dust
More information18. Stellar Birth. Initiation of Star Formation. The Orion Nebula: A Close-Up View. Interstellar Gas & Dust in Our Galaxy
18. Stellar Birth Star observations & theories aid understanding Interstellar gas & dust in our galaxy Protostars form in cold, dark nebulae Protostars evolve into main-sequence stars Protostars both gain
More informationBound Orbit of Sub-micron Size Non-spherical Silicate Dust Particles in the Dust Band of the Asteroid Belt
SUST Studies, Vol., No., ; P:-7 Bound Orbit of Sub-micron Size Non-spherical Silicate Dust Particles in the Dust Band of the Asteroid Belt M. A. Saklayen, Md. Mahmuduzzaman and M. H. Ahsan Department of
More informationChapter 10: Unresolved Stellar Populations
Chapter 10: Unresolved Stellar Populations We now consider the case when individual stars are not resolved. So we need to use photometric and spectroscopic observations of integrated magnitudes, colors
More informationLecture 2 Interstellar Absorption Lines: Line Radiative Transfer
Lecture 2 Interstellar Absorption Lines: Line Radiative Transfer 1. Atomic absorption lines 2. Application of radiative transfer to absorption & emission 3. Line broadening & curve of growth 4. Optical/UV
More informationOur View of the Milky Way. 23. The Milky Way Galaxy
23. The Milky Way Galaxy The Sun s location in the Milky Way galaxy Nonvisible Milky Way galaxy observations The Milky Way has spiral arms Dark matter in the Milky Way galaxy Density waves produce spiral
More informationThe Ṁass- loss of Red Supergiants
The Ṁass- loss of Red Supergiants Dr. Donald F. Figer Director, Center for Detectors Speaker: Yuanhao (Harry) Zhang RIT 9/12/13 1 9/12/13 2 Outline IntroducJon MoJvaJon Objects Method Need for SOFIA/FORCAST
More informationRemember from Stefan-Boltzmann that 4 2 4
Lecture 17 Review Most stars lie on the Main sequence of an H&R diagram including the Sun, Sirius, Procyon, Spica, and Proxima Centauri. This figure is a plot of logl versus logt. The main sequence is
More informationChapter 14 The Milky Way Galaxy
Chapter 14 The Milky Way Galaxy Spiral Galaxy M81 - similar to our Milky Way Galaxy Our Parent Galaxy A galaxy is a giant collection of stellar and interstellar matter held together by gravity Billions
More informationNumber of Stars: 100 billion (10 11 ) Mass : 5 x Solar masses. Size of Disk: 100,000 Light Years (30 kpc)
THE MILKY WAY GALAXY Type: Spiral galaxy composed of a highly flattened disk and a central elliptical bulge. The disk is about 100,000 light years (30kpc) in diameter. The term spiral arises from the external
More informationAstronomy 405 Solar System and ISM
Astronomy 405 Solar System and ISM Lecture 14 Comets February 15, 2013 Dynamics of Comet Tails Gas (ion) tails - interact with the solar wind - point away from the Sun. Dust tails - pushed by radiation
More informationChapter 11 Review. 1) Light from distant stars that must pass through dust arrives bluer than when it left its star. 1)
Chapter 11 Review TRUE/FALSE. Write 'T' if the statement is true and 'F' if the statement is false. 1) Light from distant stars that must pass through dust arrives bluer than when it left its star. 1)
More information5) What spectral type of star that is still around formed longest ago? 5) A) F B) A C) M D) K E) O
HW2 Name MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question. 1) The polarization of light passing though the dust grains shows that: 1) A) the dust grains
More informationStudies of diffuse UV radiation
Bull. Astr. Soc. India (2007) 35, 295 300 Studies of diffuse UV radiation N. V. Sujatha and Jayant Murthy Indian Institute of Astrophysics, Bangalore 560 034, India Abstract. The upcoming TAUVEX mission
More informationLecture # 04 January 27, 2010, Wednesday Energy & Radiation
Lecture # 04 January 27, 2010, Wednesday Energy & Radiation Kinds of energy Energy transfer mechanisms Radiation: electromagnetic spectrum, properties & principles Solar constant Atmospheric influence
More informationThe Interstellar Medium
The Interstellar Medium Fall 2014 Lecturer: Dr. Paul van der Werf Oortgebouw 565, ext 5883 pvdwerf@strw.leidenuniv.nl Assistant: Kirstin Doney Huygenslaboratorium 528 doney@strw.leidenuniv.nl Class Schedule
More informationDusty star-forming galaxies at high redshift (part 5)
Dusty star-forming galaxies at high redshift (part 5) Flow of story 4.1 4.2 4.3 Acquiring Spectroscopic or Photometric Redshifts Infrared SED Fitting for DSFGs Estimating L IR, T dust and M dust from an
More informationTracing magnetic fields through interstellar polarization
Tracing magnetic fields through interstellar polarization Nikolai Voshchinnikov Sobolev Astronomical Institute, St. Petersburg University, Russia Preliminaries: Sobolev-Chandrasekhar effect Victor Sobolev
More informationLecture 2: Introduction to stellar evolution and the interstellar medium. Stars and their evolution
Lecture 2: Introduction to stellar evolution and the interstellar medium Stars and their evolution The Hertzsprung-Russell (HR) Diagram (Color-Magnitude Diagram) Apparent and Absolute Magnitudes; Dust
More informationInterstellar grains: Effect of inclusions on extinction
Earth Planets Space, 63, 1041 1045, 2011 Interstellar grains: Effect of inclusions on extinction Nisha Katyal 1, Ranjan Gupta 1, and D. B. Vaidya 2 1 IUCAA, Post Bag 4, Ganeshkhind, Pune-411007, India
More informationThe Great Debate: The Size of the Universe (1920)
The Great Debate: The Size of the Universe (1920) Heber Curtis Our Galaxy is rather small, with Sun near the center. 30,000 LY diameter. Universe composed of many separate galaxies Spiral nebulae = island
More informationMCRT L10: Scattering and clarification of astronomy/medical terminology
MCRT L10: Scattering and clarification of astronomy/medical terminology What does the scattering? Shape of scattering Sampling from scattering phase functions Co-ordinate frames Refractive index changes
More informationCosmic Evolution, Part II. Heavy Elements to Molecules
Cosmic Evolution, Part II Heavy Elements to Molecules Heavy elements molecules First a review of terminology: Electromagnetic Electrons Element Atom Nucleus Compound Molecule Electromagnetic Strong Nuclear
More informationAstrophysics of Gaseous Nebulae and Active Galactic Nuclei
SECOND EDITION Astrophysics of Gaseous Nebulae and Active Galactic Nuclei Donald E. Osterbrock Lick Observatory, University of California, Santa Cruz Gary J. Ferland Department of Physics and Astronomy,
More informationMass loss from stars
Mass loss from stars Can significantly affect a star s evolution, since the mass is such a critical parameter (e.g., L ~ M 4 ) Material ejected into interstellar medium (ISM) may be nuclear-processed:
More informationAstro 1050 Wed. Apr. 5, 2017
Astro 1050 Wed. Apr. 5, 2017 Today: Ch. 17, Star Stuff Reading in Horizons: For Mon.: Finish Ch. 17 Star Stuff Reminders: Rooftop Nighttime Observing Mon, Tues, Wed. 1 Ch.9: Interstellar Medium Since stars
More informationExtinction & Red Clump Stars
Extinction & Red Clump Stars A NEW WAY TO ACQUIRE DISTANCES TO X-RAY SOURCES PATRICIA WROBLEWSKI UNDER THE GUIDANCE OF: DR. FERYAL ÖZEL Undergraduate Research Symposium May 8, 2008 What will be Covered
More informationPreface to the Second Edition. Preface to the First Edition
Contents Preface to the Second Edition Preface to the First Edition iii v 1 Introduction 1 1.1 Relevance for Climate and Weather........... 1 1.1.1 Solar Radiation.................. 2 1.1.2 Thermal Infrared
More informationCosmic Evolution, Part II. Heavy Elements to Molecules
Cosmic Evolution, Part II Heavy Elements to Molecules First a review of terminology: Element Atom Electro- magnetic Electrons Nucleus Electromagnetic Strong Nuclear Compound Molecule Protons Neutrons Neutral
More informationASTR-1010: Astronomy I Course Notes Section IV
ASTR-1010: Astronomy I Course Notes Section IV Dr. Donald G. Luttermoser Department of Physics and Astronomy East Tennessee State University Edition 2.0 Abstract These class notes are designed for use
More information